1. Field of the Invention
The present disclosure relates to a thermoelectric power generation unit provided with a thermoelectric conversion element converting heat into power. The present disclosure also relates to a thermoelectric power generation system provided with a plurality of thermoelectric power generation units.
2. Description of the Related Art
The thermoelectric conversion element can convert the heat into the power or convert the power into the heat. The thermoelectric conversion element made of a thermoelectric material exerting a Seebeck effect can acquire thermal energy from a heat source having relatively low temperature (for example, 200° C. or less) to convert the heat into the power. The thermal energy that is conventionally abandoned into a surrounding environment in a state of vapor, hot water, or emission gas can be recovered and effectively used in a thermoelectric power generation technology in which the thermoelectric conversion element is used.
Hereinafter, the thermoelectric conversion element made of the thermoelectric material is referred to as a “thermoelectric generator”. A general thermoelectric generator has what is called a “t-type structure” in which a p-type semiconductor and an n-type semiconductor, in which electric poralities of carriers are different from each other, are combined (for example, see Unexamined Japanese Patent Publication No. 2013-016685). In the thermoelectric generator having the “π-type structure”, the p-type semiconductor and the n-type semiconductor are electrically connected in series, and thermally connected in parallel. In the “π-type structure”, a thermal flow direction and a current flow direction are parallel or anti-parallel to each other. For this reason, it is necessary to provide an output terminal in an electrode on a high-temperature heat source side or a low-temperature heat source side. Accordingly, a wiring structure becomes complicated in order to electrically connect a plurality of thermoelectric generators having the “π-type structure” in series.
International Patent Publication No. 2008/056466 discloses a thermoelectric generator including a stacked body in which bismuth layers and metallic layers made of metal except bismuth are alternately stacked between a first electrode and a second electrode. The first electrode and the second electrode are opposed to each other. In the thermoelectric generator disclosed in International Patent Publication No. 2008/056466, a stacking plane is tilted with respect to a direction of a straight line connecting the first electrode and the second electrode. Tube-type thermoelectric generators are disclosed in International Patent Publication No. 2012/014366, Kanno et al., Proceedings of the 72nd JSAP Autumn Meeting, 30a-A-14 “Tubular power generator via off-diagonal thermoelectric effect” (2011), and A. Sakai et al., International conference on thermoelectrics 2012, 328 “Enhancement in performance of the tubular thermoelectric generator (TTEG)” (2012).